Hardening urea condensation products



Patented Sept. a, was

ENWG UREA @ONDENSA'EION IPRGDUCTS Arthur M. Howald, Pittsburgh, Pa, assignor to Toledo Synthetic Products, Inc., Toledo, Ohio, a corporation of Ohio No Drawing. Application September 26, 1930 Serial No. d8d,718

M Claims. (G1. 18-55) This invention relates to hardening urea con- There is not sufficient formaldehyde present at densation products; and it comprises an ima time when it seems, in this boiling operation, provementinprocesses of producing articles conto be needed. If urea is added to the viscous taining glassy or porcelain-like condensation liquid formed upon evaporation of the boiled liqproducts derived from urea, thiourea, substituted uid, uniform incorporation is diflicult and really ureas, etc., and formaldehyde wherein primary can only be done with a pugging mill. products so derived are hardened by an addition In the present invention I depart from the of one of the polyhydric phenols such as rescast-and-bake method of making molded artiorcinol, quinol, orcinol, pyrogallol, but advancles found in the prior art and prepare a dry tageously resorcinol, followed by a subsequent preparation which can be hot molded, that is, heating in molding under heat and pressure; all under heat. and pressure, with the production of as more fully hereinafter set forth and as claimed. sound and satisfactory products. The prepara- It has long been proposed to make condensations being dry, there is no liberation of water tion products from urea or thiourea with formvapor in the hot mold.

w aldehyde. Properly made, the final condensa- In certain prior and copending applications, tion products are of glassy nature, being indeed Serial Nos. 339,225 and 363,412, filed February 11, capable of replacing glass for many purposes 1929, and May 15, 1929, respectively, I have deand having the additional advantage that articles scribed and claimed a similar method of operacan be' machined, threaded, bored, etc. With tion in making finished articles wherein a dry the use of a filler, articles of a porcelain-like preparation is used and the final hardening is nature can be made. Commercially, however, effected in a molding press under heat and presthis art has not made much headway, because of sure; primary reaction products being converted a number of diificulties. Initial condensation is into a dry powder, this mixed with dry urea and always in the presence of water and, usually, of the mixture hot molded. Added urea or thiourea 25 more formaldehyde than is wanted in the final so admixed abbreviates hardening materially.

product. Unless the water and the formaldehyde In my copending application Ser. No. 481,807,

are efiectively removed, the final article will of which the present application is a continuation crack or craze or otherwise alter in time. Much in part, I disclose processes wherein the substanof the quality of the final article seemsto detially dried powdered primary or initial reaction pend upon minutiae in the primary condensing products of urea and formaldehyde, are mixed operation. In the usual practice, urea is diswith an added amount of urea or thiourea to prosolved in 40 per cent aqueous formaldehyde soluduce molding compositions containing such adtion and the mixture brought to a boil. A violent mixtures of materials and substantially free of reaction ensues and the mixture continues boilwater and other volatiles.

ing under its own heat evolution. Boiling is un- In another application (Serial No. 484,719, filed der a reflux condenser to maintain constant vol- Sept. 26, 1930), I have described and claimed ume and prevent loss of water andformaldehyde a method of further simplifying production of at this stage. ,Sometimes, base or acid is used as these condensation products wherein the aldea catalyst; sometimes, not. In. the standard hyde and urea are brought together and undergo method of operation, the molecular proportion of reaction in the cold; the usual high temperature formaldehyde to urea is something in excess of operation being dropped. After initial condensa- 2:1 and, after boiling is completed, the liquid is tion, the liquid material is evaporated and dried evaporated toasirupy or stifl consistency. While at a low temperature; the product being therestill liquid, it is poured into molds to form slabs after ground to a fine powder which is used as or sheets and these are baked for a long time at before, being admixed with urea or thiourea to a temperature of Bil- C. If everything is make amolding powder. An admixture of a dry right, the baked sheets can be cut into the depowder with dry urea has no tendency toward sired articles. Slabs made in this way, with reaction prior to exposure to heat in hot molding. complete dissipation of excess formaldehyde and Where fillers are used, as they generally are, of water are necessarily quite thin. they are admixed with the liquid material and the sometimes in the prior art, less proportions of evaporation and drying with production of a formaldehyde are used in the primary reaction drypowder can be much simplified. or a little more urea is added after the first vio- In any of the hereinafter described. processes, lent reaction is over; after boiling is discontinued. I have found that, in lieu of using urea to facilino Results, however, in so doing, are not very good. tate hardening, there are advantages in using hardening agents of quite another class not at all analogous to urea; that class being the polyhydric phenols.

I have found that urea present as such in the dry mixture has a tendency to react too quickly in the mold, the molding operation being made somewhatmorediflicultthereby. Thiourea,whilesomewhat better than urea in this respect, is still open to some objection. On the other hand, polyhydric phenols do not have the tendency to early reaction with exposure to heat which characterizes urea. In a wet mixture they do not react; in the mold, they react more smoothly than urea and at a more convenient speed of reaction and give a more resistant product. Resorcinol, quinol and orcinol are examples of dihydric phenols suitable in the present invention and phloroglucinol and pyrogallol are examples of useful trihydric phenols. Y I advantageously employ resorcinol. This substance produces a final product which is not quite water white but which is clear and can be delicately tinted or colored with suitable dyes or pigments. The slight color imparted by the resorcinol is not noticeable when a filler is used or when the final product is to be colored; even in delicate or pastel shades. These delicate shades may be secured by dyes incorporated in the initial aqueous mixture. The molded product is stable in the sunlight and is not affected by hot water.

In a practical embodiment of this invention, I may add urea to a heated commercial aqueous solution of formaldehyde (35 to 40 per cent). The addition of the urea causes heat to be evolved and the solution can be kept boiling by the addition of urea at the proper rate. Sufiicient urea is added to produce a ratio of about 2 moles of formaldehyde to one of urea. The solution may then be boiled under a reflux for some time and then concentrated to a thick sirup. At this time, resorcinol can be added and the mixture reduced to dryness, ground to a powder and finally molded under heat andpressure. The addition of resorcinol, etc., may be postponed and admixture made with the dry powder of the reaction product. The effect in adding resorcinol to the wet mixture and drying the mix at the usual low temperature is not greater than where the admixture of resorcinol is postponed until after a dry powder of reaction product is obtained. Plasticizers may be added at any convenient point.

In another embodiment, formaldehyde and urea, in the molecular proportions of 2:1, may be reacted together, either at room temperature or at boiling temperature. A filler maybe added to the resulting initial condensation product, resorcinol, etc., added and the mixture then dried in one of the usual drum driers. The dried product is then ground and molded as before.

I secure best results by adding a polyhydric phenol, such as resorcinol, to the primary reaction mixture in such a proportion that in the final product the molecular ratio of the aldehyde to the sum of the urea and of the polyhydric phenol varies between 1.521 and 1.75: 1.

I obtain advantageous results with as little as from 2 to 10 per cent of resorcinol by reducing the atio of formaldehyde to urea and polyhydroxy phenol, in part by adding more urea and in part by adding resorcinol.

The present invention is applicable in all processes of producing articles of hot pressed synthetic resins of the urea-aldehyde type, by which expression- I mean those resins formed by the condensation of urea, thiourea, one of the substituted ureas, cyanamid, dicyandiamid, etc., with one of the aldehydes, such as formaldehyde, acetaldehyde, furfural, acrolein, etc.

What I claim is:-

1. In the production of synthetic resin articles, the improved process which comprises condensing urea and formaldehyde in aqueous solution, removing the water, mixing a polyhydric phenol with the dried condensation product and molding the resulting mixture under heat and pressure.

2. In the production of synthetic resin articles, the improved process which comprises condensing urea and formaldehyde in aqueous solution, removing the water, mixing resorcinol with the dried condensation product and molding the resulting mixture under heat and pressure.

3. In the manufacture of molded articles under heat and pressure, the improved process which comprises reacting urea with formaldehyde in an aqueous solution to form an initial condensation product, the molecular ratio of the formaldehyde to urea being about 2:1, evaporating the solution thus obtained to dryness, mixing the dried condensation product with a polyhydric phenol, the polyhydric phenol being added in amounts sufiicient to reduce the over-all ratio ofthe formaldehyde to urea and said polyhydric phenol to between 15:1 and 1.75:1, and then molding the mixture under heat and pressure.

4. In the manufacture of molded articles from molding powders under heat and pressure, the step of preparing a molding powder which comprises mixing a polyhydric phenol with a dry powdered primary condensation product of urea and formaldehyde.

5. In the manufacture of molded articles under heat and pressure by processes involving the preparation of a molding powder, the steps which comprise forming a soluble, fusible, condensation product of urea and formaldehyde in an aqueous solution, evaporating the solution thus obtained to dryness, and mixing the dried condensation product with a polyhydric phenol.

6. In the manufacture of molded articles under heat and pressure, the process which comprises forming a condensation product of urea and formaldehyde in an aqueous solution, drying and mixing the condensation product with a polyhydric phenol, converting the dry mixture into a powder and then molding said powder under heat and pressure.

7. The process of claim 6 in which said polyhydric phenol is a dihydric phenol.

'8. The process of claim 6 in which said polyhydric phenol is resorcinol.

9. As an improved molding composition, said molding composition being a dry, fusible, molding powder free from volatiles and capable of being molded under heat and pressure to give hard, shaped, infusible, stable, molded articles in which the final over-all molecular ratio of formaldehyde to the sum of urea and polyhydric phenol is between 15:1 and 1.75:1, said powder comprising a dry powdered mixture of a polyhydric phenol and a fusible condensation product of urea and formaldehyde obtained by reacting approximately 2 mols of formaldehyde with 1 mol of urea in aqueous solution and evaporating saidsolution to dryness, the amount of the polyhydric phenol being sufiicient to reduce said overall ratio to the desired value.

10. As an improved molding composition suitable for molding under heat and pressure to give shaped, stable articles, molding powders commamas prising a polyhydric phenol and a fusible condensation product of urea and formaldehyde, said powders being substantially dry and free from volatiles.

11. The product of claim 10 in which said polyhydric phenol is a dihydric phenol.

12. The product of claim 10 in which said polyhydric phenol is resorcinol.

13. In the manufacture of molded articles under heat and pressure, the improved process vwhich comprises applying heat and pressure to a substantially dry, fusible molding composition to shape and then harden said composition, said molding composition comprising a substantially dry mixture of a polyhydric phenol and a fusible urea formaldehyde condensation product, the

said polyhydric phenol combining with and fixing any formaldehyde generated during such molding.

14. The improvement in the manufacture of molded articles from urea formaldehyde condensation products under heat and pressure which comprises molding under heat and pressure said urea formaldehyde condensation products in the presence of a polyhydric phenol, the said polyhydric phenol combining with any formaldehyde generated during molding thereby preventing the generated formaldehyde from interfering with the production of sound, solid, non-porous moldedarticles.

AR M. HOWALD. 

